Help me replace my O2 sensor

My check engine light came on, so I went to AutoZone and got the code pulled. They send it was an o2 sensor. $80 later I was on my way home. It's too damn hot to change it now, so I'm going to do it tomorrow morning. The sensor that went bad was the one before the cat on my '99 Mitsu Galant. Can anyone give me a general idea of where it is on my car?

The check engine light on my '01 Galant came on last year for the same reason. I took it to my mechanic (also a good friend of mine), and he told me what it was. He said he would get me a new 02 sensor at his cost, but there was no real reason to spend the money.

I took 4 screws out of the dash, pulled the service engine bulb, and never looked back. Car still passes emissions, and I'm up $80.

Take it back for a refund, and spend the $80 on something fun...like ammo!

It says right on the box that a working sensor is supposed to "improve fuel economy." Oddly enough, the past few months I've been getting 28 - 30 mpg with my V6. That's better than the 25 or 26 mpg the car got previously. The only things I've done in the past few months was replaced the upper radiator hose and serpentine belts. I've also been using a different oil (Napa...which they said was Valvoline bottled in their Napa bottle). I was using Castrol for several years.

The O2 sensors (there may be more than one) are located on the exhause pipe, somewhere after the "header" and before the muffler. On newer cars, there is one before and after the catalytic converter.

Since you already have the replacement, you should know what to look for, but on every car I have seen, it will be the only thing with wires attached to yout exhaust.

They make a special socket to use in removing the sensor. I highly recommend it. It looks like a standard deep well socket with 1/5 or 1/6 of the side removed to allow the wiring to poke out. The "nut" area of the sensor is usually thin.

Good luck with the install.

By the way...if there are two sensors, the first one is the important one. The second one basically just lets you know if your cat is working.

Originally posted by NOCM The O2 sensors (there may be more than one) are located on the exhause pipe, somewhere after the "header" and before the muffler. On newer cars, there is one before and after the catalytic converter.

Since you already have the replacement, you should know what to look for, but on every car I have seen, it will be the only thing with wires attached to yout exhaust.

They make a special socket to use in removing the sensor. I highly recommend it. It looks like a standard deep well socket with 1/5 or 1/6 of the side removed to allow the wiring to poke out. The "nut" area of the sensor is usually thin.

Good luck with the install.

By the way...if there are two sensors, the first one is the important one. The second one basically just lets you know if your cat is working.

+1

Also, zap the old one with a little penetrating oil if it's rusted in place. Difficulty is equivalent to changing a spark plug.

Originally posted by 10-32 The o2 sensor is just emissions rubbish. Your car does not need it.

HUH? I know for a fact that some cars use the O2 sensor to determine how much fuel to send to the injectors. I would say that's important. If you get a cracked exhaust manifold, you can actually pull air into the exhaust stream and your car will run rich cause the computer thinks it's running lean (too much O2 in the exhaust).

If you have the dual O2 sensors and the one after the catalytic converter goes out, then yeah, that is emissions rubbish.

Originally posted by nognig HUH? I know for a fact that some cars use the O2 sensor to determine how much fuel to send to the injectors. I would say that's important. If you get a cracked exhaust manifold, you can actually pull air into the exhaust stream and your car will run rich cause the computer thinks it's running lean (too much O2 in the exhaust).

If you have the dual O2 sensors and the one after the catalytic converter goes out, then yeah, that is emissions rubbish.

NN

Running without an O2 sensor will do nothing more then ruin your gas milage. At worst you engine will have a little less data to send to the FI computer to meter fuel porperly, you're computer learns as you drive, so day to day stuff you usually don't see any problems, however if you travel to an elevation extreme you may notice back smoke out the tail pipe as the rig will be over fueling. Also, fuel injection systems have alot of redundency built into them, manufacturers don't want people stranded when one sensor goes bad. Running without an 02 sensor could compound the problems if another one is lost. That being said, I replace any O2 sensor when it goes bad, and if you were going to do the same I highly recommend the special socket for it, it make life much easier. Good luck!

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I know quite a bit about International Trucks and Tractors, but little about Glocks, kinda why I am here:D!

Replace the sensor. This ain't the old days where you could rip off the emissions crap and get better performance. The sensor is very important. You'll run on "Closed Loop" without it. Kinda like running your CHOKE all the time. They should actually be replaced every 50,000 miles or so (my '98) maybe the newer ones last longer with the heating elements in them to clean off the sensor. Use a little Anti-Sieze on the threads.
O-R-H

ETA: Use the cars engine to warm up the pipe SOME before you loosen it. You could also heat the bung with a propane torch to loosen the threads.